LONDON, May 1 (Reuters) - Britain’s financial regulator has banned a former senior UBS trader for failing to blow the whistle on colleague Kweku Adoboli, the “rogue trader” jailed in 2012 for running up $2.3 billion in unauthorised trading losses.

Announcing its first ban from regulated financial jobs for such a failure, the Financial Conduct Authority (FCA) said on Thursday John Hughes had been aware of Adoboli’s actions but had failed to challenge him, report him or act as a role model with “catastrophic consequences”.

“Instead he ... allowed the desk’s profit and loss to be misstated over an extended period,” FCA enforcement and financial crime division head Tracey McDermott said.

“This failure contributed to Adoboli’s unauthorised trading continuing unchecked. Approved people should operate to the highest standards of integrity.”

Between January and September 2011, Hughes was the most senior person on UBS’s Exchange Traded Funds desk at the London branch of UBS - a period during which Adoboli ran up such hefty trading losses that they that risked undermining the Swiss bank.

Adoboli was sentenced to seven years in jail in November 2012 for two counts of fraud by abuse of position. Shortly afterwards, the FCA fined UBS 29.7 million pound ($50 million) for systems and controls failures.

Hughes - who was dismissed for gross misconduct weeks after Adoboli’s arrest - wept in court in October 2012 after reading an email in which his former colleague admitted to the trades.

Part of the unauthorised trading involved creating and using a secret fund, dubbed the “Umbrella”, which had the effect of manipulating the desk’s reported profit and loss.

The FCA said Hughes knew about the existence of the Umbrella, how it was being used, did not consider it to be honest and knew UBS would not have authorised its use.

Although Hughes felt “a bit sick” when he first learned about the existence of the Umbrella, the FCA said he soon ensured he was regularly told about its size and became involved in decisions about how to fund and use it.

“Hughes’ conduct in relation to the Umbrella was dishonest and demonstrates that he is not a fit and proper person to perform functions in relation to any regulated activity carried on by an authorised or exempt person,” the FCA said.

British authorities are keen to encourage whistleblowing as they attempt to develop a corporate culture of integrity and restore faith in financial markets.

British law firm Pinsent Masons said it had FCA data that showed the number of whisteblowing reports had risen by 64 percent to an average 556 per month since the FCA took over from the Financial Services Authority (FSA), in April 2013. ($1 = 0.5922 British pounds) (Editing by Louise Ireland)